The invention relates to a connecting device for a pipe or like fluid conduit, with a coupling body and a clamping collar which can be set into a substantially cylindrical recess of the coupling body in an axially inner starting position and into which, for example after such setting into the recess, one end of the pipe to be connected can be slid, for example, until its front-side abuts a stop of the coupling body. The clamping collar comprises at its inner end at least one radially displaceable arresting tongue, which, when the pipe, and therewith the clamping collar, is slid back in a direction of a recess inlet, for example under pressure building up in the pipe coupling, up into an axially outer arresting position, can be pressed radially inwardly and with its inner side into engagement with an outer wall surface of the pipe through cooperation of an outer side of the arresting tongue with a first slope, radially slanting in the direction of the recess inlet, of an inner wall surface of the coupling body. In this way a plug connection between the pipe or the like fluid conduit can be established and detached simply and rapidly.
In FIG. 1 is depicted in section such a commercially available connecting device in section. In order to produce tightness between connecting devices, between the outer wall surface of the pipe and the inner wall surface of the coupling body an O-ring seal is provided in the recess of the coupling body at the front side of the inner end of the clamping collar. To detach the plug connection, the clamping collar can be slid for example with the aid of an outer flange, from the axially outer arresting position, depicted in FIG. 1, further into the recess of the coupling body up into its axially inner starting position, whereby arresting tongues of the clamping collar spread out of their radially inwardly pressed position due to cooperation with the sealing ring and, optionally, their own reset force and can release again a pipe end. It has been found that, on the one hand, into gaps between the pipe end and clamping collar, as well as between the clamping collar and coupling body, moisture and dirt can penetrate from outside, which makes detaching the plug connection difficult and, on the other hand, when producing and detaching the plug connection scratches and like damage are generated in an outer wall surface of the pipe end, whereby leaks occur under fluid pressure obtained in the connecting device. Based on recognition that these problems occur in practice, an apparent solution was to additionally seal, on the one hand, the pipe end against the clamping collar and, on the other hand, the clamping collar against the coupling body adjacent to the recess inlet, as has also been proposed in EP 1 143 185 A1, with aid of two O-ring seals. Of these two O-ring seals, one is provided between the clamping collar and an inner wall surface of the coupling body, and the other one is provided between the clamping collar and an outer wall surface of the pipe.
However, one problem is still a reliable spreading open of the arresting tongues when the clamping collar is slid in from the arresting position depicted in FIG. 1, since, on the one hand, compliance of a sealing ring at a front side of the clamping collar after ageing and, on the other hand, in absence of sufficient resilient elasticity, a reset force of the resilient tongues do not ensure an adequate spreading out force.